Uplink interference mitigation method and apparatus

ABSTRACT

Disclosed is a method and apparatus for mitigating uplink interference in the wireless communication system, wherein the method comprises determining a loading-status value for each sector; if the loading-status value is not greater than the first threshold value, generating UL zone switch IE and UL allocation start IE to allocate data bursts of the sectors to different subchannels; and preparing an uplink map using the UL zone switch IE and UL allocation start IE for each sector, wherein the uplink duration indicates a duration where all the subchannels are used for allocation of the data burst.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of application Ser. No. 12/922,440 filed Dec. 6,2010, which is a national stage application of PCT International PatentApplication No. PCT/KR2009/001203 filed Mar. 11, 2009 and claims thebenefit of Korean Patent Application 10-2008-0022627 filed Mar. 11,2008, the disclosure of which is incorporated herein its entirety byreference.

BACKGROUND

Field of the Invention

The present invention relates to a wireless communication system, andmore particularly, to a method and apparatus for mitigating uplinkinterference in the wireless communication system.

Discussion of the Related Art

Based on a proposed standard of IEEE (Institute of Electrical andElectronics Engineers) 802.16, BWA (Broadband Wireless Access)supporting OFDMA (Orthogonal Frequency Division Multiplexing Access)allows to transmit much information in a short time owing to a broadbandfrequency, wherein the frequency in one frequency band is divided and isthen efficiently used by plural users.

This wireless communication system one-dimensionally allocates databursts for an uplink duration except a predetermined region in a symbol(time)-first order. That is, if the data burst allocation is completedfor all subchannels in a certain symbol, the data burst allocation isstarted for the subchannels in the next symbols. This method impliesthat all the subchannels for each sector are used for the data burstallocation.

However, as shown in FIG. 1, if the data burst is allocated to all thesubchannels in each sector for the uplink duration, interference mayoccur by the neighboring sectors. In order to overcome this problem, ifa cell loading factor is equal to or greater than a predetermined value,as shown in FIG. 2, the data burst is allocated to all the subchannelsfor each sector, and a permbase value for permutation of the sector isdifferently set for each sector. Accordingly, the inter-sectorinterference is averaged out for each subchannel, and thus theinterference of the neighboring sectors is mitigated. If the cellloading factor is less than the predetermined value, as shown in FIG. 3,a method has been proposed for mitigating the interference among thesectors by differently setting a subchannel region to be allocated withthe data burst for each sector, and setting the same permbase value ineach sector for permutation.

For mitigating the interference for the uplink duration by theaforementioned method, it is required to dynamically change theaforementioned set information to define the data burst allocationregion according to the cell loading status.

However, the aforementioned set information may be formed with TLV(Type, Length, Value) such as UL allocated subchannels bitmap or UL AMCallocated physical bands bitmap. However, the aforementioned TLV isincluded in UCD (Uplink Change Descriptor). That is, if theaforementioned set information is changed, considerable time is neededuntil the changed set information is applied to each mobile station.Eventually, it is difficult to efficiently mitigate the sectorinterference for the uplink duration.

SUMMARY

Accordingly, the present invention is directed to a method and apparatusfor mitigating uplink interference that substantially obviates one ormore problems due to limitations and disadvantages of the related art.

Technical Solution

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein,there is provided an uplink interference mitigation method in an uplinkduration comprising: determining a loading-status value for each sector;if the loading-status value is not greater than the first thresholdvalue, generating UL zone switch IE and UL allocation start IE toallocate data bursts of the sectors to different subchannels; andpreparing an uplink map using the UL zone switch IE and UL allocationstart IE for each sector, wherein the uplink duration indicates aduration where all the subchannels are used for allocation of the databurst.

In addition, the method further comprises allocating the data burst ofthe sectors by using the subchannels defined by the UL zone switch IEand UL allocation start IE.

The step of generating the UL zone switch IE and UL allocation start IEcomprises: setting a subchannel use type and permbase value included inthe UL zone switch IE; and setting a subchannel offset included in theUL allocation start IE.

If the loading-status value for each sector is equal to or smaller thanthe first threshold value, and simultaneously larger than the secondthreshold value, some of the sectors are set with the same permbasevalue, and the subchannel use type of the sectors is set to use all thesubchannels during setting the permbase value and subchannel use type;and the subchannel offset is differently set for each of the sectorswith the same permbase value during setting the subchannel offset.

The sector to be set with the different permbase value is changed everyframe.

Also, the sector to be set with the different permbase value isdetermined as the sector where a mobile station with high CINR (Carrierto Interference Noise Ratio) is positioned.

If the loading-status value for each sector is not greater than thesecond threshold value, all the sectors are set with the same permbasevalue, and the subchannel use type of the sectors is set to use all thesubchannels during setting the permbase value and subchannel use type;and the subchannel offset is differently set for each of the sectorsduring setting the subchannel offset.

The subchannel offset of the sectors is determined by the ratio of thenumber of sectors and the number of subchannels.

The subchannel offset of the sectors is determined by the ratio of thenumber of sectors and the number of subchannels, and the loading-statusvalue for each sector.

All the subchannels are used as the data burst allocation region for theuplink duration through the use of at least one of UL allocatedsubchannels bitmap or UL AMC allocated physical bands bitmap included ina UCD message.

In another aspect of the present invention, there is provided an uplinkinterface mitigation method in an uplink duration comprising:determining a loading-status value for each sector; if the loading-statevalue is larger than the first threshold value, generating UL zoneswitch IE to allocate data bursts of the sectors to all subchannels; andpreparing an uplink map of each sector through the use of UL zone switchIE, wherein the uplink duration indicates a duration where some of thesubchannels among all the subchannels are used for allocation of thedata burst.

In another aspect of the present invention, there is provided an uplinkinterference mitigation apparatus comprising: a UCD message generatingmeans which generates a UCD message defining that all subchannels for anuplink duration are used as data burst allocation regions; aloading-status determining means which determines a loading-status valuefor each sector; and a map message generating means which generates ULzone switch IE and UL allocation start IE to allocate data bursts todifferent subchannels for the respective sectors, and allocates thegenerated UL zone switch IE and UL allocation start IE to a UL-MAPregion of each sector, when the loading-status value of each sector isnot greater than the first threshold value.

In another aspect of the present invention, there is provided an uplinkinterference mitigation apparatus comprising: a UCD message generatingmeans which generates a UCD message defining that some of subchannelsfor an uplink duration are used as data burst allocation regions; aloading-status determining means which determines a loading-status valuefor each sector; and a map message generating means which generates ULzone switch IE and UL allocation start IE to use all the subchannels ofthe sectors, and allocates the generated UL zone switch IE and ULallocation start IE to a UL-MAP region of each sector, when theloading-status value of each sector is larger than the first thresholdvalue.

In another aspect of the present invention, there is provided an uplinkinterference mitigation method comprising: setting a value of UL zoneswitch IE to indicate whether a subchannel allocation region of anuplink duration is changed or not according to an interference level;setting a value of UL allocation start IE to indicate a starting pointof the subchannel allocation region of the uplink duration; andtransmitting a UL-MAP message generated using the UL zone switch IE andUL allocation start IE.

In another aspect of the present invention, there is provided an uplinkinterface mitigation method comprising: receiving a UL-MAP messageincluding a value of UL zone switch IE and a value of UL allocationstart IE, wherein the value of UL zone switch IE indicates whether asubchannel allocation region of an uplink duration is changed or notaccording to an interference level, and the value of UL allocation startIE indicates a starting point of the subchannel allocation region of theuplink duration; and allocating a UL data burst to a subchannel definedby the UL-MAP message.

In another aspect of the present invention, there is provided an uplinkinterference mitigation method comprising: generating a UP-MAP messageto change at least one of the number or position of subchannels used foran uplink duration according to a cell loading status; and transmittingthe UP-MAP message.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

Advantageous Effects

The method and apparatus for mitigating uplink interference according tothe present invention enables to mitigate the UL interference.

Also, the subchannel allocation may be dynamically changed to mitigatethe UL interference.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an interference for an uplink duration;

FIG. 2 illustrates a related art interference mitigation method when adata burst is allocated to all subchannels for an uplink duration;

FIG. 3 illustrates a related art interference mitigation method when adata burst is allocated to some of subchannels for an uplink duration;

FIG. 4 is a block diagram illustrating an uplink interference mitigationapparatus according to one embodiment of the present invention;

FIG. 5 illustrates a subchannel offset for each segment, which iscalculated by a loading factor for each segment;

FIG. 6 is a flow chart illustrating an uplink interference mitigationmethod according to one embodiment of the present invention; and

FIG. 7 is a flow chart illustrating an uplink interference mitigationmethod according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings.

FIG. 4 is a block diagram illustrating an uplink interference accordingmitigation apparatus to one embodiment of the present invention. Asshown in FIG. 4, the uplink interference mitigation apparatus 200includes a UL channel descriptor (hereinafter, referred to as ‘UCD’)message generating means 210, a loading-status determining means 220,and a map message preparing means 230.

The UCD message generating means 210 generates a UCD message to beallocated to a UCD region, wherein the UCD message defines a region tobe allocated with a data burst for an uplink duration.

The UCD message generating means 210 according to one embodiment of thepresent invention may creat the UCD message to define all or some ofsubchannels for the uplink duration as the data burst allocation region.

According to one embodiment of the present invention, the UCD messagegenerating means 210 generates the UCD message including TLV (Type,Length, Value) of UL allocated subchannels bitmap or UL AMC allocatedphysical bands bitmap, to define the region to be allocated with thedata burst for the uplink duration.

In more detail, if all the subchannels for the uplink duration of eachsector are defined as the data burst allocation region by using the TLVof UL allocated subchannels bitmap or UL AMC allocated physical bandsbitmap, a permbase value for each sector may be differently set so as tomitigate the sector interference. In the embodiment of the presentinvention, the UL allocated subchannels bitmap, UL AMC allocatedphysical bands bitmap, and permbase value for each segment may bedefined as the following Table 1.

TABLE 1 UL Segment 0x00 0x00 0x00 0x00 0x07 0xFF 0xFF 0xFF 0xFFallocated 0 shbchannels Segment 0x00 0x00 0x00 0x00 0x07 0xFF 0xFF 0xFF0xFF bitmap 1 Segment 0x00 0x00 0x00 0x00 0x07 0xFF 0xFF 0xFF 0xFF 2 ULAMC Segment 0x000000 FFFFFF Allocated 0 physical Segment 0x000000 FFFFFFbands 1 bitmap Segment 0x000000 FFFFFF 2 Permutation Segment x base 0Segment x + 1 1 Segment x + 2 2

In above Table 1, the segment corresponds to each sector. Forconvenience of the explanation, supposing that one cell comprises threesectors, and the three sectors correspond to ‘segment 0’, ‘segment 1’,and ‘segment 2’. As shown in above Table 1, all the subchannels are usedfor the data burst allocation region for each segment. The UL PUSC zoneuses the TLV of UL allocated subchannels bitmap, and uses the 35subchannels. The BAND AMC uses the TLV of UL AMC allocated physicalbands bitmap, and uses the 24 bands.

Also, the permbase values are differently set for the respectivesegments.

If trying to define some of the subchannels of the uplink duration foreach segment as the data burst allocation region through the use of TLVof UL allocated subchannels bitmap or UL AMC allocated physical bandsbitmap, the UL allocated subchannels bitmap, UL AMC allocated physicalbands bitmap, and permbase value for each segment may be defined as thefollowing Table 2.

TABLE 2 UL Segment 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x0F 0xFFallocated 0 shbchannels Segment 0x00 0x00 0x00 0x00 0x00 0x00 0xFF 0xF00x00 bitmap 1 Segment 0x00 0x00 0x00 0x00 0x07 0xFF 0x00 0x00 0x00 2 ULAMC Segment 0x000000 0000FF Allocated 0 physical Segment 0x000000 00FF00bands 1 bitmap Segment 0x000000 FF0000 2 Permutation Segment x base 0Segment x 1 Segment x 2

In above Table 2, if the region to be allocated with the data burst isdifferently set for each segment through the use of TLV of UL allocatedsubchannels bitmap in the UL PUSC zone, the ‘segment 0’ uses subchannelsfrom 0 to 11, the ‘segment 1’ uses subchannels from 12 to 23, and the‘segment 2’ uses subchannels from 24 to 34.

If the region to be allocated with the data burst is differently set foreach segment through the use of TLV of UL AMC allocated physical bandsbitmap in the UL Band AMC zone, the 8 bands are defined as the databurst allocation region for each segment.

In this case, the permbase value for each segment is set identically.

The UCD message generating means 210 sets the region to be allocatedwith the data burst for the uplink duration in each segment through theuse of TLV of UL allocated subchannels bitmap or UL AMC allocatedphysical bands bitmap, and generates the UCD message including the TLVto be allocated to the UCD region.

The loading-status determining means 220 receives information about thedata bursts to be transmitted from an upper layer, and determines theloading status of each segment and the loading status of the cellaccording to the size of the data bursts to be transmitted. Herein, theloading means virtually-allocated resources among total usableresources.

The loading status of each segment and the loading status of the cellaffect the interference among the segments. Thus, it is for dynamicallychanging the subchannel allocated with the data burst according to theloading status. This is why the loading status of each segment and theloading status of the cell are determined.

According to one embodiment of the present invention, the loading-statusdetermining means 220 determines the loading status every frame or everyscheduling period. At this time, the loading-status determining means220 calculates a loading factor of each segment and a loading factor ofthe cell by using a ratio of the total number of usable slots and thenumber of slots required by the scheduling result, and then determinesthe loading status according to the loading ratio. In consideration tothe uplink duration, the total number of usable slots may be calculatedby the following Equation 1.

$\begin{matrix}{{{the}\mspace{14mu}{total}\mspace{14mu}{number}\mspace{14mu}{of}\mspace{14mu}{usable}\mspace{14mu}{slots}} = {{the}\mspace{14mu}{number}\mspace{14mu}{of}\mspace{14mu}{subchannels}\; \times \;\frac{{the}\mspace{14mu}{number}\mspace{14mu}{of}\mspace{14mu}{symbols}}{3}}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

The loading factor of the cell may be calculated by adding the loadingfactors of the segments.

The map message generating means 230 generates a MAP message allocatedin MAP region for the uplink duration. Generally, an uplink MAP messageincludes information about uplink bursts. If it is needed to change thedata burst allocation region based on the cell loading status determinedby the loading-status determining means 220, the map message generatingmeans 230 according to one embodiment of the present invention generatesinformation elements (IE) to change the data burst allocation region inthe MAP message.

In case that, all the subchannels for the uplink duration are set as thedata burst allocation region in the UCD message for each segment, andthe cell loading factor determined by the loading-status determiningmeans 220 is not greater than a predetermined threshold value, the databurst is allocated to part of the all available subchannels for eachsegment, instead of allocating the data burst to all the subchannels. Inthis case, preferably, the data burst allocation region is differentlyset for each segment, to thereby realize the improved efficiency.

The map message generating means 230 prepares UL zone switch IE and ULallocation start IE in the map region, whereby the data burst allocationregion is changed from all of the subchannels to part of the allavailable subchannels.

In this case, the construction of UL zone switch IE is shown in thefollowing Table 3, and the construction of UL allocation start IE isshown in the following Table 4.

TABLE 3 Syntax Size Notes UL_Zone_IE ( ) {  Extended UIUC 4 UL_Zone =0x04  Length 4 Length = 0x03  OFDMA symbol offset 7 0b00 = PUSCpermutation 0b10 = Adjacent subcarrier permutations 0b11 = Reserved Permutation 2  UL_Permbase 7  AMC Type 2 Indicates the AMC type in casepermutation type = 0b10, otherwise shall be set to 0. AMC type (NxM = Nbins by M symbols): 0b00 - 1x6 0b01 - 2x3 0b10 - 3x2 0b11 - Reserved Use All SC Indicator 1 0 = Do not use all subchannels 1 = Use allsubchannels  Disable subchannel 5 Only applies to PUSC permutation rotation (see section 8.4.6.2.6) 0 = subchannel rotation enabled 1 =subchannel rotation disabled  reserved 4 }

In above Table 3, ‘OFDMA symbol offset’ indicates an offset of an OFDMAsymbol where the corresponding zone is to be started, wherein an offsetvalue is defined by the unit of symbol. Also, ‘permutation’ indicatesthe permutation used for allocation of the data burst according to theUL zone switch IE, wherein the permutation is used as a base value forpermutation of UL permbase value.

‘Use All SC Indicator’ indicates whether all the subchannels are used ornot. If it is ‘0’, it indicates that the subchannels defined by thesubchannel bitmap included in the UCD message are used. In the meantime,if it is ‘1’, it indicates that all the subchannels are used.

TABLE 4 Syntax Size Notes UL Allocation start IE ( ) {  Extended UIUC 4UL_Allocation_start_IE( ) = 0x0A  Length 4 Length = 0x02  OFDMA symboloffset 8 This value indcates start symbol offset of all subsequent ULallocations in this UL_MAP message (UL-MAP or SUB-UL-DL-MAP). Thereference point of this offset is the start of UL sub-frame.  Subchanneloffset 7 This value indicates start subchannel offset of all subsequentUL data burst allocations in this message (UL-MAP or SUB-UL-DL-MAP). reserved 1 Shall be set to zero. }

In above Table 4, ‘UL allocation start IE’ includes the OFDMA symboloffset and subchannel offset, whereby the subchannel offset isdifferently set for each segment.

Hereinafter, a method for generating the aforementioned UL zone switchIE and UL allocation start IE according to the cell loading status bythe map message generating means 230 will be described in detail asfollows.

First, if the loading factor for each segment determined by theloading-status determining means 220 is not greater than the firstthreshold value, for example, it is not greater than about ⅓, thepermbase value included in the UL zone switch IE is identically set foreach segment by the map message generating means 230. That is, if thepermbase value of ‘segment 0’ is ‘x’, the permbase value of each of‘segment 1’ and ‘segment 2’ is set as ‘x’. Also, the value of ‘Use AllSC Indicator’ included in the UL zone switch IE is set as ‘1’, wherebyall the subchannels are used.

Then, the subchannel offsets for the segments included in the ULallocation start IE are differently set by the map message generatingmeans 230. In one embodiment of the present invention, the subchanneloffset of each segment may be calculated by the number of subchannelsand the number of segments, that is, the subchannel offset of eachsegment may be calculated by the following Equation 2.

$\begin{matrix}{{{subchannel}\mspace{14mu}{offset}} = {{round}\mspace{11mu}\left( \frac{{the}\mspace{14mu}{number}\mspace{14mu}{of}\mspace{14mu}{subchannels}}{{the}\mspace{14mu}{number}\mspace{14mu}{of}\mspace{14mu}{segments}} \right)\; \times \;{segment}\mspace{14mu}{number}}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

Herein, ‘round( )’ indicates that the value included in ( ) is roundedoff.

For example, if the number of subchannels in the UL PUSC zone is 35, andthe number of segments is 3; the subchannel offset of ‘segment 0’becomes the subchannel 0, the subchannel offset of ‘segment 1’ becomesthe subchannel 12, and the subchannel offset of ‘segment 2’ becomes thesubchannel 24.

In a modified embodiment of the present invention, the subchannel offsetfor each segment may be calculated by using the loading factor of eachsegment. For example, if the loading factor of ‘segment 0’ is ⅔, and theloading factor of ‘segment 1’ and ‘segment 2’ is ⅙; the subchannelscorresponding to ⅔ of the total subchannels are allocated for the‘segment 0’, and the remaining subchannels are uniformly distributed andallocated for the ‘segment 1’ and ‘segment 2’, as shown in FIG. 5.

The map message generating means 230 prepares the UL zone switch IE andUL allocation start IE by setting the identical permbase value and thedifferent subchannel offsets for the respective segments. Thus, the databurst is allocated to the different subchannels for each segment, tothereby decrease the interference among the segments.

If the loading factor of each segment, which is determined by theloading-status determining means 220, is greater than the firstthreshold value and smaller than the second threshold value, forexample, if the segment loading factor is between ⅓ and ½, the mapmessage generating means 230 sets the identical permbase value includedin the UL zone switch IE for the two segments, and sets the differentpermbase value for the remaining one segment. For example, the permbasevalue for each of the ‘segment 0’ and ‘segment 1’ is identically set as‘x’, and the permbase value for the ‘segment 2’ is set as ‘x+1’. Also,the value of ‘Use All SC Indicator’ indicating the subchannel use typeis set as ‘1’ so that all the subchannels are used.

In case of the subchannel offset included in the UL allocation start IE,the different subchannel offsets are set for the two segments with theidentical permbase value. In this case, the subchannel offset for thesegments with the identical permbase value may be calculated by thefollowing Equation 3.

subchannel  offset=                         [Equation  3]${round}\mspace{11mu}\left( \frac{{{the}\mspace{14mu}{number}\mspace{14mu}{of}}\mspace{14mu}{subchannels}}{\begin{matrix}{{{the}\mspace{14mu}{number}\mspace{14mu}{of}\mspace{14mu}{segments}}\mspace{14mu}} \\{{with}\mspace{14mu}{the}\mspace{14mu}{same}\mspace{14mu}{permbase}\mspace{14mu}{value}}\end{matrix}} \right) \times {segment}\mspace{14mu}{number}$

For example, the number of subchannels in the UL PUSC zone is 35, andthe permbase value is identically set for the ‘segment 0’ and ‘segment1’; the subchannel offset of ‘segment 0’ is determined as ‘0’, and thesubchannel offset of ‘segment 1’ is determined as ‘18’ by the aboveEquation 3.

The subchannel offset for the remaining one segment with the differentpermbase value applied thereto may be set as ‘0’. In a modifiedembodiment of the present invention, if satisfying that all thesubchannels in the segment with the different permbase value appliedthereto are defined as the data burst allocation region, the subchanneloffset may be set as any other value as well as ‘0’.

According to one embodiment of the present invention, the interferencemitigation hardly occurs in the segment with the different permbasevalue applied thereto. In this respect, the segment with the differentpermbase value applied thereto may be rotated, or the segment to beprovided with the different permbase value may be determined as thesegment where a mobile station with high CINR (Carrier to InterferenceNoise Ratio) exists.

Meanwhile, in case that some of the subchannels may be used in eachsegment for the uplink duration for the data burst allocation region inthe UCD message, and the entire cell loading factor determined by theloading-status determining means 220 is larger than a predeterminedthreshold value, it is efficient to allocate the data burst to all thesubchannels and to average out the interference among the segmentsthrough the permutation. Accordingly, the map message generating means230 prepares the UL zone switch IE to allocate the data burst to all thesubchannels for the uplink duration in each segment of the map region.

In more detail, if the cell loading factor determined by theloading-status determining means 220 is larger than the predeterminedthreshold value, the map message generating means 230 sets the differentpermbase values to the segments included in the UL zone switch IE, andalso sets the value of ‘Use All SC Indicator’ as ‘1’ to thereby use allthe subchannels for each segment.

The map message generating means 230 sets the different permbase valuesfor each segment, and sets the subchannel use type to use all thesubchannels, to thereby allocate the data burst to all the subchannelsfor each segment, and simultaneously to decrease the interference amongthe segments by averaging the interference through the permutation usingthe different permbase values.

The UCD message generated by the aforementioned UCD message generatingmeans 210 and the map message generated by the map message generatingmeans 230 are transmitted to the mobile station managed by acorresponding base station. Then, the mobile station receiving the UCDmessage and map message from the corresponding base station allocatesthe UL data burst to the data burst allocation region defined by the UCDmessage and map message.

In more detail, if the UCD message received in the mobile station fromthe base station indicates that the data burst is allocated to all thesubchannels for the uplink duration, the data burst is allocated to allthe subchannels. Also, if the map message received in the mobile stationfrom the base station includes the UL zone switch IE and UL allocationstart IE, the data burst is allocated to the subchannels defined by theUL zone switch IE and UL allocation start IE.

If the UCD message received in the mobile station from the base stationindicates that the data burst is allocated to some of the subchannelsfor the uplink duration, the data burst is allocated to some of thesubchannels. Also, if the map message received in the mobile stationfrom the base station includes the UL zone switch IE, the data burst isallocated to all the subchannels defined by the UL zone switch IE.

As mentioned above, the subchannels may be dynamically changed byallocating at least one of the UL zone switch IE and UL allocation startIE to the map region according to the cell loading status, to therebymitigate the uplink interference with high efficiency.

For the aforementioned explanation, the uplink interference mitigationapparatus according to the embodiment of the present invention includesthe plural means which are separately provided to carry out their ownfunctions. However, a modified embodiment of the present invention maydisclose a multi-functional integrated means.

A method for mitigating the uplink interference will be described withreference to FIGS. 6 and 7.

FIG. 6 is a flow chart for explaining the uplink interference mitigationmethod in case of the UCD message defining that the data burst isallocated to all the subchannels for the uplink duration.

As shown in FIG. 6, the loading factor of each segment is calculated bythe data burst information received from the upper layer (S400). In thiscase, as mentioned above, the loading factor of each segment may becalculated by the ratio of the total number of usable slots and thenumber of slots required by the scheduling result. In one embodiment ofthe present invention, the loading factor may be determined every frameor every scheduling period.

If the loading factor of each segment is high, the interference becomesworse among the segments. In this respect, the loading factor of eachsegment is calculated so as to dynamically change the subchannelsallocated with the data burst according to the loading status of eachsegment.

Then, the loading factor of each segment is compared with thepredetermined threshold value (S410). Based on the comparison result, ifthe loading factor of each segment is not greater than the predeterminedthreshold value, the UL zone switch IE and UL allocation start IE areprepared to allocate the data burst to the different subchannels foreach segment (S420).

In one embodiment of the present invention, if the loading rate of eachsegment is not greater than ⅓; the permbase value of the segmentincluded in the UL zone switch IE is identically set for each segment,the value of ‘Use All SC Indicator’ is set as ‘1’, and the subchanneloffsets for the segments included in the UL allocation start IE are setdifferently. In this case, the subchannel offset for each segment may becalculated by the above Equation 2.

In another embodiment of the present invention, if the segment loadingfactor is between ⅓ and ½, the permbase value included in the UL zoneswitch IE is identically set for the two segments, and is differentlyset for the remaining one segment, wherein the value of ‘Use All SCIndicator’ for all the segments is set as ‘1’. Also, the subchanneloffset in the two segments with the same permbase value may be setthrough the above Equation 3, and the subchannel offset in the remainingone segment with the different permbase value may be set as ‘0’. At thistime, if satisfying that all the subchannels in the segments with thedifferent permbase value are defined as the data burst allocationregion, the subchannel offset may be set as any other value as well as‘0’.

Then, the map message is generated to allocate the UL zone switch IE andUL allocation start IE to the map region of each segment frame (S430).

The UCD message and map message generated by the aforementioned processare transmitted to the mobile station. Thus, the mobile stationreceiving the UCD message and map message sequentially allocates thedata burst to all the subchannels defined by the UCD message. If the mapmessage includes the UL zone switch IE and UL allocation start IE, thedata burst is sequentially allocated to the subchannels defined by theUL zone switch IE and UL allocation start IE.

FIG. 7 is a flow chart for explaining the uplink interference mitigationmethod according to another embodiment of the present invention, whereinthe UCD message defines that the data burst is allocated to some of thesubchannels for the uplink duration.

As shown in FIG. 7, the cell loading factor and the loading factor ofeach segment are calculated by the data burst information received fromthe upper layer (S500). In this case, as mentioned above, the cellloading factor and the loading factor of each segment may be calculatedby the ratio of the total number of usable slots and the number of slotsrequired by the scheduling result. In one embodiment of the presentinvention, the loading factor may be determined every frame or everyscheduling period.

As explained in S400 of FIG. 6, the loading rate of each segment iscalculated because the segment interference is affected by the loadingstatus of each segment. In this respect, the loading factor of eachsegment is calculated so as to dynamically change the subchannelsallocated with the data burst according to the loading status of eachsegment.

Then, the loading factor of each segment is compared with thepredetermined threshold value (S510). Based on the comparison result, ifthe loading factor of each segment is larger than the predeterminedthreshold value, the UL zone switch IE may be prepared to use all thesubchannels on the data burst allocation for each segment (S520).

In more detail, if the loading factor of each segment is larger than thepredetermined threshold value, the permbase value included in the ULzone switch IE is differently set for all the segments, and the value of‘Use All SC Indicator’ indicating the subchannel use type is set as ‘1’.All the subchannels are used for each segment through the aforementionedsetting. However, the permbase values for the segments are setdifferently so that the interference is mitigated by averaging.

The UL zone switch IE is allocated to the map region of each segmentframe, to thereby prepare the map message (S530).

According to the aforementioned process, the generated UCD message andmap message are transmitted to the mobile station. Then, the mobilestation receiving the UCD message and map message sequentially allocatesthe data burst to some of the subchannels defined by the UCD message. Ifthe UL zone switch IE is included in the map message, the data burst issequentially allocated to all the subchannels defined by the UL zoneswitch IE.

The aforementioned uplink interference mitigation method may be embodiedin type of program performed through the use of various computer means.At this time, the uplink interference mitigation method is recorded in acomputer-readable recording medium, for example, hard disc, CD-ROM, DVD,ROM, RAM, or flash memory.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. An uplink interference mitigation methodperformed by a base station (BS) in a communication system comprising:allocating, for a mobile station, a first set of frequency resourceunits related to a sector, wherein the first set of frequency resourceunits correspond to at least one bit position of a physical band bitmap;acquiring load information including load information of a neighboringsector, the load information being associated with interferenceoccurring in uplink, wherein the load information associated with theinterference is based on an interference level; determining whether theinterference level is higher or lower than a threshold value; setting asecond set of frequency resource units for the mobile stationdifferently from the first set of frequency resource units if there is athird set of frequency resource units having the interference levelhigher than the threshold value; and performing uplink scheduling forthe mobile station within the second set of frequency resource units,wherein the uplink scheduling includes allocating, for the mobilestation, the second set of frequency resource units related to thesector with avoiding the third set of frequency resource units relatedto the neighboring sector based on the load information.
 2. The methodof claim 1, further comprising: transmitting information on allocationof the first set of frequency resource units to the mobile station; andtransmitting information on allocation of the second set of frequencyresource units to the mobile station.
 3. The method of claim 1, whereinthe load information is updated in a predetermined time.
 4. The methodof claim 3, wherein the predetermined time is a frame or schedulingperiod.
 5. An apparatus for a base station (BS) performing uplinkinterference mitigation in a communication system comprising: aprocessor; a receiver; and a transmitter, wherein the processor isconfigured to: allocate, for a mobile station, a first set of frequencyresource units related to a sector wherein the first set of frequencyresource units correspond to at least one bit position of a physicalband bitmap; acquire, using the receiver, load information includingload information of a neighboring sector, the load information beingassociated with interference occurring in uplink, wherein the loadinformation associated with the interference is based on an interferencelevel; determine whether the interference level is higher or lower thana threshold value; set a second set of frequency resource units for themobile station differently from the first set of frequency resourceunits if there is a third set of frequency resource units having theinterference level higher than the threshold value; and performinguplink scheduling for the mobile station within the second set offrequency resource units, wherein the uplink scheduling includesallocating, for the mobile station, the second set of frequency resourceunits related to the sector with avoiding the third set of frequencyresource units related to the neighboring sector based on the loadinformation.
 6. The apparatus of claim 5, the processor is furtherconfigured to: transmit, using the transmitter, information onallocation of the first set of frequency resource units to the mobilestation; and transmit, using the transmitter, information on allocationof the second set of frequency resource units to the mobile station. 7.The apparatus of claim 5, wherein the load information is updated in apredetermined time.
 8. The apparatus of claim 7, wherein thepredetermined time is a frame or scheduling period.